MONOCEROS. 1 95 



M. ENGONATUM, Conr. PI. 61, fig. 304. 



Whorls with a carinated shoulder, with revolving striae and 

 intervening, more or less interrupted, chocolate-brown narrow 

 bands. Aperture white within, lip thickened and dentate. 



Length, '8-1-25 inches. 



California, from Bolinas Bay to Kan Diego. 



This is the most northern in distribution of three California 

 species, which are evidently of common derivation. Mr. Stearns, 

 who is excellent authority, considers them distinct, although so 

 very closely related, and as I find that I can place every specimen 

 of the numerous individuals before me in its appropriate species, 

 I acquiesce in this arrangement. 



The Pur pur a spirata of Blainv. is evidently the same species 

 as engonatum and would have precedence according to date of 

 publication, but Conrad's name is so well known in connection 

 with the species that I am unwilling to drop it. Mr. Stearns has 

 designated under Blainville's name what he calls a local variety 

 from San Diego, but it does not seem to me to have sufficient 

 character. 



M. LAPILLOIDES, Conrad. PI. 61, fig. 305. 



Shell oval, not shouldered, last whorl inflated, aperture wide, 

 canal very short. Covered with revolving riblets and interrupted 

 chocolate bands or series of square spots ; aperture chocolate, 

 but little thickened within the lip, and with or without slight 

 teeth. Length, -75-1 inch. 



Monterey to Catalina Island, California. 



M. PAUCILIRATA, Stearns. PI. 61, fig. 308. 



Somewhat shouldered ; body-whorl with four or five narrow 

 revolving raised ribs, the interstices of which are chocolate-brown, 

 and generally broken up into squares ; aperture light-chocolate, 

 slightly toothed within the outer lip. Length, '5-' 6 inch. 



Coronado Isles, off San Diego, Cal. , to Todos Santos Bay, L. Cal. 



Much smaller than the two preceding forms, with fewer revol- 

 ving ribs and larger tessellations. 



